The Fallout 4 modding community have done many interesting mods. You can be a Jedi, you can wear weird hats and so on. All this is viable thanks to the huge modding community. While you can find many interesting mods at http://www.nexusmods.com/fallout4/? , one of the most interesting mods that have been released to date is the one that allows you to play as Dogmeat, your dog companion and one of the many companions in the world of Fallout 4.
You can find the mod here: http://www.nexusmods.com/fallout4/mods/11094/?
It is very customizable. You can use different models of dogs. They are the same game models of dogs you can meet throughout your traveling in the Fallout 4. Since you are a dog, you will have to fight as one! So, the mod has 4 types of attack you can use.
Here's a video overview of the mod: